Torque converter



March 2, 1954 E. J. THURBER TORQUE CONVERTER 2 Sheets-Sheet 1 Filed May 6, 1949 3mm (Edu/arcl'IThurbw ATTORNEYS March 2, 1954 E. J. THURBER TORQUE CONVERTER 2 Sheets-Sheet 2 Filed May 6, 1949 (lug/cord J. Thurber ATTOR N EY S Patented Mar. 2, 1954 TORQUE CONVERTER Edward J. Thurber, New Orleans, La., assignor to The Thurber Corporation, New Orleans, La., a

corporation of Louisiana Application May 6, 1949, Serial No. 91,793

Claims. 1

This invention relates to hydraulic torque converters and more particularly to a variable speed fluid transmission of the type wherein the torque is multiplied and the power is transmitted through the cooperation between an impeller or drive member, a fluid guide member, a turbine or driven member, and the circulation of a working fluid in a closed path through such members.

In conventional hydraulic torque converters, the fluid exhausted from the impeller is delivered directly to the turbine from whence it flows through a stationary fluid guide member. This latter member functions to reverse the direction of flow of the working fluid and to-deliver the same back to the impeller. Thus the fluid is caused to traverse a toroidal working path which interlinks the impeller, turbine and fluid guide members. Since however, the pattern of the fluid exhausted from the turbine varies in relation to the speed of rotation of the turbine, it has been found that a point is reached where such fluid pattern is not suchthat the fluid will pass smoothly and efliciently through the fixed profile of the blades or vanes of the fluid guide member. Such a variation in the flow of the fluid causes an overfeeding of the fluid guide member, an underfeeding of the impeller, and an undesirable turbulence in the fluid working circuit, which results in the generation of a considerable amount of heat and an appreciable loss in efliciency.

It is also customary in the hydraulic torque converters heretofore proposed, to position the fluid guide member in a rather restricted area located near the center of the fluid working circuit and closely adjacent the axis of the rotating members. With such an arrangement, the effective dissipation of the heat generated in the fluid is rendered exceedingly diiiicult. In addition, the fluid must reverse its direction of flow in a relatively small area, thus further contributing to the loss inefficiency through a partial blocking of the fluid circuit and a consequent generation of heat.

Accordingly, one of the principal objects of the present invention is to provide a hydraulic transmission of the torque converter type which is so constructed and arranged as to avoid the objections and disadvantages above set forth.

Another object is to provide a novel hydraulic torque converter wherein the fluid exhausted from the impeller is delivered directly to a stationary fluid guide member, the latter being so constituted that the reversal of the direction of the fluid flowing through the fluid guide member will take place in a, relatively substantial area, in

a gradual and smooth manner, and without the eneration of excessive heat.

A further object is to provide in a torque converter of the above character, a novel construction wherein the stationary guide member, the turbine and the impeller all cooperate with the working fluid to cause the turbine to rotate in a direction opposite to that of the impeller, and to impart a directional flow characteristic to the fluid exhausted from the turbine and delivered to the impeller, which is the same as the direction of rotation of the impeller.

Another object resides in positioning the stationary guide member radially outwardly of the impeller and turbine elements, thus materially increasing the area in which the fluid flow is reversed and greatly simplifying the problem of the efiective dissipation of any heat generated in the working fluid.

A further object is to provide a novel control for the guide member and casing therefor so that the guide member may be selectively allowed to freely rotate, to be driven with the impeller, or to be held in a stationary position.

Stil1 another object relates to a novel arrangement for selectively withdrawing the working fluid from cooperation with the impeller and turbine members, thus effectively interrupting the transmission of torque between these members, such arrangement being also such as to permit the re-establishment of the working circuit at the will of the operator.

A still further object comprehends a, novel torque converter assembly of the foregoing type wherein the casing and fluid guide member may be rotated manually when the parts are at rest, this construction materially facilitating the filling, draining, flushing and other servicing operations for the unit.

A further object is to provide a novel control for the torque converter which may be selectively operated for causing an output shaft associated with the converter to be rotated in one direction for reverse operation or the opposite direction for forward operation, such control being of such nature as to avoid the use 01' toothed gears or devices of a similar construction.

A still further object is to provide a fluid transmission and control of the above character which includes relatively few parts, the construction and arrangement thereof being such as to provide a compact and readily controllable structure, and

one which functions at a relatively high emciency. Other objects and novel features of the invenaevaazs tion will appear more fully hereinafter from a consideration of the following detailed description when taken in connection with the accom panying drawings illustrating one form of the invention. It is to be expressly understood however, that the drawings are utilized for purposes of illustration only and are not to be taken as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein similar reference characters refer to similar parts throughout the several views,

Fig. 1 is a side view partly in section of a hydraulic power transmission device embodying the principles of the present invention;

Fig. 2 is a partial sectional view of the device taken substantially along line 2-2 of Fig. 1; and

Fig. 3 is a View similar to Fig. 2 but taken substantially along line 3-3 of Fig. 1.

Referring more particularly to Fig. 1, the novel hydraulic transmission device of the present invention is illustrated therein as being of the torque converter type and includes a fluid unit H] which is arranged to drivably connect driving and driven shafts i 2 and M, respectively, the driving shaft being rotatably supported by a front bearing !5 carried by a fined casing section i8, and the driven shaft being mounted for rotation in a rear casing 29 as by means of a bearing 22.

As shown, the driving shaft 12 is provided at its forward end with a plurality of splines 24 for driving an impeller member 26 through a sleeve 28. At its rear end, the driving shaft (2 is splined at 39 to a driving clutch member 32 and is hollow bored at 34 to slidably receive the forward end of the driven shaft M, it being pointed out that the intermediate portion of said driving shaft l2 passes freely through the central bore of a turbine member 36 and a turbine driven sleeve 31.

One of the novel features of the present invention resides in the construction and arrangement of the fluid unit it which provides a simplified torque converter structure capable of operation in a highly efficient manner. More particularly, the fluid unit l0 includes the impeller and turbine members and 36, respectively, together with a fluid guide member constituted by a housing or casing 40 for the reception and guidance of the working fluid, the casing being formed of a forward casing section 42 and a rear casing section 44, such casing sections being secured together as by a plurality of screws 45. At its forward end, the casing section 62 is formed with a sleeve 48 which is rotatably supported upon the impeller sleeve 28 by a bearing 50, a combined clutch and brake member 52 being slidably splined at 54 to the exterior of the sleeve 48 for a purpose which will appear more fully hereinafter. The rear casing section M is also provided with a sleeve 55 which extends between and is rotatably supported by the turbine driven sleeve 3! and a bearing 58 carried by a fixed partition forming a part of the rear casing 20. It will be observed from the foregoing that the impeller and turbine members 26 and 35, respectively, are coaxially aligned and arranged side by side, while the periphery of the casing 40 constituting the fluid guide member, is positioned radially outwardly of the impeller and turbine members and surrounds the latter. Due to this construction, the fluid guide member provides a substantial area which not only facilitates the change of the direction of the flow of fluid, as

4 the latter is exhausted from the impeller 26 and delivered to the turbine 36, but also enables the effective dissipation of the heat generated in the fluid during operation of the unit.

In order to provide for the efficient transfer of torque through the fluid unit l0, and referring to Figs. 2 and 3, the impeller is provided with an intake manifold 62 at its central portion and a plurality of curved vanes or blades E l at its peripheral portion. As shown, such blades are angularly directed with respect to the radii of the impeller so that the inner ends 66 thereof are positioned in advance of the outer ends 69 thereof as respects the direction of rotation of the impeller as denoted by the arrows E. Such direction of rotation is counterclockwise when viewing the device from the direction indicated by the arrow C in Fig. 1. It will also be noted that the blades 64 are slightly curved in order to present a concave surface to the fluid as the latter flows radially outwardly from the manifold 52 during rotation of the impeller.

For the purpose of receiving the fluid from the impeller 26 and redirecting and delivering the fluid to the. turbine 36, each of the casing sections 42 and 44 of the fluid guide member 40 are provided with spaced apart matched guide vanes or blades 10 and H of equal area, which are substantially radially directed as clearly shown in Figs. 2 and 3. However, the blades H of the rear section 44 of the fluid guide member are curved slightly in a direction opposite to the direction of rotation of the impeller, as indicated at 2 in Fig. 3. Due to this construction, as the fluid is exhausted from the blades 'H of the rear section 44, the direction of flow thereof will be clockwise as indicated by the arrows J of Fig. 3 and thus'the turbine 36 will be caused to rotate in a direction opposite to that of the impeller.

A further important feature of the invention is to provide an arrangement whereby the direction of flow of the fluid exhausted from the turbine will be the same as the direction of rotation of the impeller. In this manner turbulence of the fluid and the excessive generation of heat will be avoided. Referring to Fig. 3, it will be observed that the fluid exhausted from the rear section 44 of the fluid guide member is directed in a clockwise direction and will strike the sur faces of a plurality of curved blades or vanes M formed at the peripheral portion of the turbine 36. As shown, the blades H are shaped in such a manner that as the fluid is exhausted from the turbine 36, it will flow to the impeller intake manifold 62 in a direction generally along the lines indicated by the arrows K, or in a counterclockwise direction. This direction of flow of the fluid is identical with the direction of rotation of the impeller. Hence, by the novel construction proposed, all abrupt changes in the direction of the flow of the fluid in the working circuit are avoided and a directional flow characteristic is imparted to the fluid as it is exhausted from the turbine which is similar to the direction of rotation of the impeller.

In addition to the foregoing, a further important feature of the invention resides in a novel construction for controlling the effectiveness of the fluid working circuit which, in normal operation during the transmission of torque, flows in a toroidal path interlinking the impeller 25, the fiuidguide member 40 and the turbine 35, as denotedby the arrows F, Fig. 1. Such novel construction'includes a selectively operable lever 16 which may be operated to one of thre positions for rotating the fluid guide memberwith the impeller 26, for locking the member 40 to a stationary part, or for allowing the member 46 to freely rotate. More particularly, and referring to Fig. l, the lever I6 is pivotally mounted to the casing I8 through a pin I8 so as to be capable of selective movement to one of the three positions indicated at S, N or R. At its lower end 88, the lever I6 engages a yoke 82 which is connected with the clutch and brake member 52, which latter, it will be recalled, is slidably splined to the casing section 42 of thefluid guide member 4i! so as to be rotatable with the latter. In the neutral position N, as shown, the member 52 is positioned intermediate a drive clutch 84, which is splined to the driving shaft, and a stationary brake member 86 which is connected with the casing I8. Under these conditions, and with the impeller 26 at rest, it will be readily seen that the fluid guide member 40 may be readily rotated by hand in order to facilitate the filling, draining, flushing or other servicing operations for the fluid unit I8.

In the event that the impeller 26 is rotating and it is desired to establish the fluid working circuit F for the transmission of torque, the control lever I6 is moved to the stationaryor S position in order to bring the clutch and brake member 52 into frictional engagement with the stationary brake member 86. This action effectively locks the fluid guide member 48 in a stationary position to allow the flow of the working fluid in the manner heretofore described.

Should it be desired to interrupt the transmission of power through the fluid unit I0, at any time during operation, it is only necessary to move the lever I6 to the rotate or R position. When this movement is effected, the fluid guide member 48 will be rotated by the diving shaft I2 through the frictional engagement between the driving clutch 84 and the clutch and brake member 52. As soon as this occurs, all the fluid entering the periphery of the casing 40 in the area of the fluid guide blades III and II will, under the influence of centrifugal force be forced radially outward, and as long as the casing 40 is rotated there can be no radial inward flow of the fluid, and thus the fluid circuit is effectively interrupted. The above operation will occur in the event that the amount of liquid in the fluid unit It! may all be received within the region of the guide member 49 defined by the blades I0 and II, when the guide member is rotated. With the working fluid thus withheld from cooperation with the impeller and turbine members, it will be readily understood that the transmission of torque between such members is effectively interrupted. Due to this construction, the necessity of a separate disconnectible clutch between the driving and driven members of the transmission is avoided. It will be understood, that as soon as the control lever "I6 is again moved to the stationary or S posiiton, the casing II) will be held stationary and the fluid will automatically return to the impeller and turbine members so that the working circuit F may be reestablished and the transmission of torque resumed. Preferably suitably frictional facing are provided on the cooperable faces of the members 52, 84 and 86 in order to provide eincient clutching and braking actions. It 'is also preferred that the blades II! and II of the fluid guide member 49 be cut away slightly to provide an annular passage or port 88 so that the fluid may be properly distributed in the fluid guide member 40 when the latter is rotated as above described. I i

Novel means are" provided for selecting and controlling the direction of rotation of the driven shaft I 4, so that the latter may be rotated for forward or reverse operation. In the-form of the invention illustrated, such means includes a selecting-lever 90 which is pivoted by a pin 92 to the stationary casing 20 so as to be capable of pivotal'movement to anyone of the positions indicated at N, R or F. At its lower end 94, the lever engages a yoke 96 which. is secured to the driven shaft I4 through a pin 98, so that any pivotal movements of the lever will cause axial movements of the shaft I4.

In order to control the direction of rotation of the shaft I4 in accordance with axial movements thereof, the said shaft is provided with a clutch member III!) which, when the lever 90 cccupies the "neutral position N, is spaced slightly from the driving clutch 32 and a driving yoke I82. As shown, the latter includes forward and rear sections IM and I06 which are connected togetheras by means of a plurality of screws I08. The rear section I06 is provided with a sleeve III'I which is interposed between the shaft I4 and the bearing 22. The forward section I04 is splined at H0 to the turbine sleeve 31, and the latter is driven from the turbine 36 through a one-way clutch of well known type comprising inner and outer rings H2 and I I4 having a plurality of wedging rollers H6 disposed therebetween. With such an arrangement, it will be understood that as the turbine is rotated in the direction E, Fig. 3, under the influence of the working fluid, the outer ring I I4 will cause the rollers H6 to become wedged against the inner ring II 2 in order to establish a driving connection between the turbine 36 and the sleeve 31. On the other hand, should the sleeve 31 be connected with the driven shaft, and the latter tend to overrun the turbine 36, free wheeling of the driven shaft will result from the use of the oneway clutch. Moreover the one-way clutch will permit the turbine 36 to freely rotate in an opposite direction from that indicated by the arrows H of Fig. 3, in the event that the transmission of power is interrupted by moving the lever I6 to the position R as heretofore described. In such event, the impeller and the free runring turbine both rotate in the same direction. It will be understood that suitable frictional facings are provided on the engaging surfaces of the members 32, I00 and I06, as shown.

From theabove, it will be readily seen that withthe fluid unit in operation, should the lever 90 be moved to the forward or F position, the clutch III!) will be moved into frictional engagement with the rear portion I86 of the yoke I82 in order to establish a forward drive connection between the turbine 36 and the driven shaft I4 by-way of the one-way clutch H4, H6 and H2, the sleeve 37, the yoke I62 and the clutch mem-' ber I66. Such forward drive will be constituted through the fluidunit V ID. on the other hand should itbe desired to establisha reverse or direct drive, the lever 90 is moved to the reverse or R position in order to connect the driven shaft I4 directly with the driving shaft I2 by way of the clutch members I00 and 32. In this case, the fluid unit I0 is shunted, and the drive is direct from the driving shaft I2 to the driven shaft I4.

It is to be pointedout that when desirable, the

lever I6 at the forward end of the fluid unit III andathedeyerrimzatztheereanendzofitherunitimaio be so connected that when the lever 9llhiszmovecl tor; connect. the: clutch; Hi; to; the: direct; drive clutch: 3-22 the lever; 'IB'aWill; be: simultaneously or coincidentally operatedl to bring:- the clutch 52'; intozengagement with-the: drivingrclutoh' 84. It wilizbe clearrth'at". duringzthiss. operation, the: cats-- ing 42: will; beconnected; with the driving: shaft l2: to:.be rotatedthereby: to thus: stopthe; fluid from being circulatedorragitated-and:at:the same time, thesdriving shaft. I2? willi'be directlyrcone nected with' the drivemshaft Hi.

In operation; and: assuming" that: the parts of: the transmissionare' at restwithi the' levers: 16 and 90 occupying the neutral or; N; positions; it: will; be= understood? that. the fluid* guide: member 40 maybe freely manuailyxrotated for any. requiredf servicing operations: Hence; a. suitable: quantity of'working: fluid inarr amount required to=establish1the fluid:circuit -F; whenethe impelleris rotating, may: be poured into the-- member at: through: a flller plug; not shownyin order-to conditioni the unit IDE for: thetransmission. of torque: Thereafter the shaft I2 is rotatedby: anyrsuita-ble' means, suchasuthe power plant on airautomotive vehicle.

In: order-to place the fluid unit: lflfin operation, it is onlyrneoessaryvto move thalever lBi to the S positiorr in' order: to hold the" fluid guide member: MI; stationary: through the cooperation betweenwthe brake and clutchimember 52 and the brake member- 88; Thereupon thetoroidal'path of the fluid working circuitiF is established and the turbine- 36 will be rotated in i a direction opposite-to the direction of rotation of the impeller 26;- it-being: noted from Figs: 2 and 3 that the impeller member 2K rotates in: the direction of the arrows=E while=the=turbine 3'6'rotates in the opposite-direction as showrrby the arrows H;

With the parts in suclicondition, the shifting 'lever'fll) may be operatedtoselect the desired direction of rotation of the Y drivenshaft l 4. Forexample; in the event that it is desired to rotate the driven shaft l'k'in the same direction as lie turbinetli the lever-Sil willbe moved to the position F which, through: the shifting of the yoke 96; shaft I4 andclut'cli member lllllto the right, as viewed in Fig; 1; will establish a driving connectionwith the turbine 36 by-way of the onezvay-clutohconnection H4; H6 and H2, the turbine driven sleeve 31', theyoke I 04, and the clutch member Hlir'secured tothedriven shaft I4. Under these conditions, the shaft llwillbe directly driven in the samedirection as the direction of rotation of the turbine -36 and'the drive will include allof the members of the fluid unit Ill.

On the other hand; should itbedesiredto rotat'e-the driven'shaft l4 intheopposite direction, it is:onl'yneoessaryto move the Shifting lever 90 to the-position' Rin orderto bring the clutch member 100 into direct frictional engagement with thedriving clutch 32. Due to this operation; it will be readilvunderstood that the; driving and drivenshafts are directly connected together'independently of the fluid unit it), by way of ,the drivingclut'chl32.andi,the clutch member mo. which is secured or, otherwise connected with thedrivenishaft.

lt'ewillybenoted from the abovethat thecontrol of; the. directiom of, rotationZ of:- the. driven shaft. IA is; effected by- & simplermanioulation I of.- the shifting lever 90 and without the necessity? of; employing toothed; gearsion their equivalents. Such-anlarraneementavoidsallclashing ofr ears 4B: and; the turbine: iii-will be? established and maintained; Duringgthe operation of the'fluid unit, the; blades; 64 of, the? impeller willcause the. fluid torbe withdrawn; from I the; intake manifold? (it and; to: flow radially outWardly-where-it; is ref-l T ceived=by5 the; blades of the fluidjguidemembera 40; While. passing; through; theblades 10: and- 'H-, the;direction@ofrthmfluidwillbereversed-andtherfluitt will thereafter bedelivered to the :bladed' turbine 35 along; the paths JV; Fig; 3., such" paths being directedin;themannerillustrated, by reaa somofithezcurved inner ends 1210f the blades; Hz

Thusthesfluid lea-vingl the blades 1 I- of; therfluidguide member 49 will be: flowing in a. clockwise direction, as viewed-inFig; 3; andiwill cause'the turbine: to rotate: in: aw similaridirection which. is; opposite to: the? direction; of rotation of theimpeller:

The fluid, inipassingthrough-the bladesldiofthe turbine; will-follow the :contour-ofzthese blades and will-.be:- exhausted in adirection indicated by the arrows-K Fig. 3: Such direction-of flow is the-same as the direction of rotation of the; impeller and; henceall? overcrowding; or under-w feeding-of thee-latter is:avoided;

W hen it; is.desiredito interrupt the transmission ofoowenthroughthe fluid unit 10 and; thereby,- deolutch the; driving; and; driven shafts; theselectinge1ever--16 is moved to :the 1R position in or:- der t0= connect: the; fluid guide member 40: di+ rectly; with the driving; shaft? I-Z-' through: the driving; clutch: Standathei clutch andbrake mem ber; 52. As, soon: as-v this oecurs,- and the: fluid guidefmember; 40 is: rotated, thefluidwill flowinto the -b-laded-area or the: guide member under; the influenceof centrifugalforce; and will re-'-- main-thereduring oontinuedrrotation of the guidemember; Thus, assoon as the turbine is deprivedi of; fluid; a; declutohing; action is secured, and the-.turbine-will-.be freeto rotate ina counterclockwise direction, asviewed in Fig; 3; this action-being; possible due to;the: provision of the one-way, clutchjoonnection 1 l4, M ii and H 2-.

the foregoing, it willbe observed: that when-theiamount ofrfluid in the fluidiunitlil'issuch that-all of; it v may: b' vreeeived withinthe area'defined: bu thefiblades it and H thetrans-- missionwoftorque betWeen-thedriving and riven shafts.- may be interrugted by rotating the guide member; Interruptionof the torquemay also be: effected: in the eventi that; theguide; member; 4a contains van: amount: of fluid inexcess; of that whichmay;be-accommodated3b3t the area defined by the: blades 1.0 and H. In' suchdatter event;- when: the-guideemember lfl isrotated; the turbiner36 wilhbe free to -rotaterinzthe same-direct tion as the impeller zfirdue to the, releasing action of the one-wayolutch: I I2, H4 and H6;

It! will, be understood that the; resumption of the-transmission oftpowermay 'be readily effected by merely'moyingthe-selecting lever 16 back to thefiiuosition in order;- to render. the fluid guide memberr'staticmam: When this occurs, thegfiuid' is; returnedtoithe impeller: and turbine members and: 13115? fluidmorkingoircuit (E is-- rel-established. The presentzinrention; thus provides a novel:

hydraulic power transmission of the torque converter type which includes a highly desirable construction of impeller, turbine and fluid guide members, positioned, shaped and arranged to avoid any underfeeding or crowding of such members during the operation of the fluid working circuit. In addition, the provision of the control for the fluid guide member secures a simplified arrangement for either maintaining the guide member stationary for power transmission, or for rotating the same to provide an effective control of the fluid working circuit for declutching. A further feature resides in theselective control of the output of the transmission unit which is arranged to secure rotation of the output shaft in either direction without the use of toothed gears or their equivalents.

It will be readily understood that while one embodiment of the invention has been shown and described herein, various modifications may be resorted to without departing from the spirit of the invention. For example, instead of a radial flow of the fluid from the impeller and to the turbine by way of the fluid guide member, it is contemplated that such a flow may be lateral if desired. Those skilled in the art will perceive various other modifications and changes without departing from the essence of the invention. Ref erence will therefore be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. A fluid power transmission mechanism comprising a single rotatable casing containing a working fluid, a driving shaft, an intermediate shaft, a driven shaft, means for rotatably mounting said casing with respect to said shafts, said casing having a plurality of circumferentially arranged and spaced apart fluid guide vanes occupying the area of the periphery of the easing, said fluid guide vanes having an equal area on each side of a center line arranged transverse to the axis of rotation of the casing and which divides the casing into two similar parts, clutch and brake means for respectively selectively connecting the casing to said driving shaft for rotation thereby or to a stationary part to hold the casing stationary, an impeller in said casing, means for connecting the impeller to said driving shaft for rotation thereby to circulate the fluid in the casing, a single turbine element having a single turbine wheel fixed against axial movement in said casing and positioned in the path of the circulating fluid to be rotated thereby, said fluid guide vanes being positioned in the path of the circulating fluid between the impeller and the turbine wheel and arranged to reverse the direction of fluid flow, said turbine wheel having a plurality of vanes positioned and arranged to cause the turbine wheel to rotate oppositely to the direction of rotation of the impeller when the fluid is flowing therethrough, means including a one-way clutch connecting said turbine wheel and said intermediate shaft to transmit torque to the latter when the turbine wheel is under the influence of the circulating fluid and allowing the turbine wheel to freely r0- tate in the same direction of rotation as the impeller when the casing is rotated, and means for connecting the intermediate and driven shafts.

2. A fluid power transmission mechanism as set forth in claim 1 wherein the circulation of fluid in the casing by the impeller moves radially outwardly from the impeller into and through the fluid guide vanes where the fluid is turned radially inwardly to flow into and through the turbine wheel, the turbine wheel vanes being directed to cause the fluid which is exhausted therefrom to flow in the same direction as the direction of rotation of the impeller.

3. A fluid power transmission mechanism as I set forth in claim 1 which includes in addition,

means for connecting the driven shaft with the driving shaft.

4. A fluid power transmission mechanism as set forth in claim 3 which includes in addition, means operable to selectively connect the casing with the driving shaft for rotation therewith when the driving and driven shafts are connected.

5. A fluid power transmission mechanism as set forth in claim 1 which includes in addition, a shiftable clutch movable in one direction to connect the driven shaft with the intermediate shaft to rotate the driven shaft in one direction, and movable in the other direction to connect the driven shaft with the driving shaft to rotate the driven shaft in the opposite direction.

EDWARD J. THURBER.

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